Photopolymerization, i.e., polymerization induced by light, is used to convert a liquid monomer or macromer to a polymer using visible or ultraviolet radiation. Some types of cross-linked hydrophilic polymers known as hydrogels may be formed in vivo using photopolymerization. These hydrogels exhibit good biocompatibility, making them attractive materials for use in a variety of biomedical applications.
Formation of photopolymerized hydrogels in vivo can be accomplished using bulk or interfacial photopolymerization. In bulk photopolymerization, a photoinitiator is dissolved in a hydrogel precursor (prepolymer) solution. A photoinitiator is a material that has a high absorption at a specific wavelength of light to produce radical initiating species that convert a prepolymer to a polymer. Upon exposure to an appropriate wavelength of light, the hydrogel precursor and photoinitiator solution is converted to the hydrogel state.
In interfacial photopolymerization, a photoinitiator is adsorbed onto the surface of tissues or cells. Eosin photoinitiators are commonly used because of their high affinity for tissues. A prepolymer, in this case a hydrogel precursor solution, is then delivered to the site, and the site is exposed to an appropriate light source. Polymerization occurs at the tissue interface, where the hydrogel precursor is in contact with the adsorbed photoinitiator.
Interfacial photopolymerization may be used to form thin hydrogel linings on various tissue surfaces, including the inner walls of vessels carrying bodily fluids. Dual occlusion catheters are currently used to deliver photoinitiators and prepolymers to target vessels. The treatment cavity formed between the two balloons must be filled with each component, requiring a relatively large amount of material. For example, typically about 3 milliliters of a prepolymer is required to fill the cavity, even though only a fraction of the material is converted into a hydrogel coating on the wall of the vessel. In addition, complications can occur if the vessel is occluded for more than 60 seconds. This may require the clinician performing the procedure to rush in order to avoid damage to the vessel and other complications when using a dual occlusion catheter.
Therefore, it would be desirable to have an improved catheter-based photopolymerization system and treatment method that overcome the aforementioned and other disadvantages.